JP2014005193A - Optical member, image pickup device, and method for manufacturing optical member - Google Patents

Abstract

An optical member including a porous glass layer on a base material with suppressed ripples, a method for easily manufacturing the optical member, and an imaging device for capturing an image transmitted through the optical member. An imaging apparatus is provided.
An optical member comprising a substrate 1 and a porous glass layer 2 formed on the substrate 1, wherein the concavo-convex structure is formed at an interface contacting the porous glass layer 2 of the substrate 1. The height of the concavo-convex structure formed is not less than 100 nm and not more than the thickness of the porous glass layer 2. The height of the concavo-convex structure is 250 nm to 1000 nm, and the width of the concavo-convex structure is 100 nm to 2000 nm.
[Selection] Figure 1

Description

  The present invention relates to an optical member including a porous glass layer on a base material, an imaging device including the optical member, or a method for manufacturing the optical member.

  In recent years, porous glass is expected for industrial use such as adsorbents, microcarrier carriers, separation membranes, optical members, and the like. In particular, porous glass is widely used as an optical member because of its low refractive index.

  As a comparatively easy method for producing porous glass, there is a method utilizing a phase separation phenomenon. As a base material of a porous glass using a phase separation phenomenon, borosilicate glass made of silicon oxide, boron oxide, alkali metal oxide or the like is generally used. This borosilicate glass is heat-treated at a constant temperature to cause phase separation into a silicon oxide rich phase and a non-silicon oxide rich phase (hereinafter referred to as phase separation treatment), and the non-silicon oxide rich phase is eluted with an acid solution (hereinafter referred to as “phase separation treatment”). Manufacturing the porous glass. The skeleton constituting the porous glass produced in this way is mainly silicon oxide. The skeleton diameter, pore diameter, and porosity of the porous glass affect the light reflectance and refractive index.

  Non-Patent Document 1 discloses a configuration in which the elution of the non-silicon oxide rich phase is partially insufficient in etching, the porosity is controlled, and the refractive index increases from the surface toward the inside. The reflection on the surface of the porous glass is reduced.

  On the other hand, Patent Document 1 discloses a method of forming a porous glass layer on a substrate. Specifically, a film containing borosilicate glass (phase-separable glass) is formed on a substrate by a printing method, and a porous glass layer is formed on the substrate by phase separation treatment and etching treatment. ing.

Japanese Patent Laid-Open No. 01-083583

J. et al. Opt. Soc. Am. , Vol. 66, no. 6,1976

  When the porous glass layer is formed on the substrate as a few μm as in Patent Document 1, the light incident on the surface of the porous glass is reflected between the surface of the porous glass and the substrate and the porous glass. Since the reflected light at the interface interferes, ripples (interference fringes) are generated.

  Non-Patent Document 1 does not disclose any configuration for forming a porous glass layer on a substrate. Furthermore, in the method of Non-Patent Document 1, since it is difficult to control the degree of progress of etching, it is difficult to control the refractive index, and the non-silicon oxide rich phase that is a soluble component remains, resulting in a decrease in water resistance. Problems in use as an optical member such as cloudiness occur.

  An object of the present invention is to provide an optical member having a porous glass layer on a substrate, in which ripple is suppressed, and to provide a method for easily manufacturing the optical member.

  The optical member of the present invention is an optical member comprising a base material and a porous glass layer formed on the base material, and has an uneven structure at an interface contacting the porous glass layer of the base material. The height of the concavo-convex structure is not less than 100 nm and not more than the thickness of the porous glass layer.

  The method for producing an optical member of the present invention is a method for producing an optical member comprising a base material and a porous glass layer formed on the base material, and a base material having an uneven structure is prepared. And a step of forming a porous glass layer on the surface of the concavo-convex structure of the substrate, wherein the concavo-convex structure has a height of the concavo-convex structure of 100 nm or more and the thickness of the porous glass layer. It is characterized by the following.

  According to the present invention, it is possible to provide an optical member including a porous glass layer on a base material, in which ripple is suppressed, and a method for easily manufacturing the optical member.

Cross-sectional schematic diagram showing an example of the optical member of the present invention Illustration explaining ripple Diagram explaining porosity Diagram explaining average pore diameter and average skeleton diameter Schematic showing an imaging device of the present invention Sectional schematic diagram for demonstrating an example of the manufacturing method of the optical member of this invention Plane schematic diagram showing an example of an uneven structure provided on the optical member of the present invention Cross-sectional SEM image of the optical member produced in Example 1 Cross-sectional SEM image of the optical member produced in Comparative Example 1 The figure which shows the wavelength dependence of the reflectance of Examples 1-9 The figure which shows the wavelength dependence of the reflectance of Comparative Examples 1-3 The figure which shows the relationship between an uneven structure, an Example, and a comparative example Diagram showing an example of a porous structure derived from spinodal phase separation Diagram showing an example of a porous structure derived from binodal phase separation Cross-sectional schematic diagram for explaining an example of the step of forming the concavo-convex structure on the substrate Cross-sectional SEM image of the optical member produced in Example 10 The figure which shows the wavelength dependence of the reflectance of Examples 10-16

  Hereinafter, the present invention will be described in detail with reference to embodiments of the present invention. For parts not specifically shown or described in the present specification, well-known or well-known techniques in the art are applied.

  The “phase separation” in the present invention will be described by taking as an example the case where a borosilicate glass containing an oxide having silicon oxide, boron oxide, or alkali metal is used for the glass body. “Phase separation” refers to a phase containing non-silicon oxide rich phase and non-silicon oxide-rich phase containing alkali metal and glass oxide inside the glass, and an alkali metal oxide and boron oxide. It means separating into a phase (silicon oxide rich phase) containing less than the composition before separation. And the porous structure is formed in a glass body by etching the glass which carried out phase separation, and removing a non-silicon oxide rich phase.

  There are two types of phase separation: spinodal and binodal. Porous glass structures using phase separation include a porous structure derived from spinodal type phase separation and a porous structure derived from binodal type phase separation. The porous structure derived from the spinodal type phase separation and the porous structure derived from the binodal type phase separation are judged and distinguished from the result of morphological observation by a scanning electron microscope (SEM). Specifically, the cross-sectional observation of the porous glass layer is performed at a magnification of 150,000 times at an acceleration voltage of 5.0 kV using a scanning electron microscope (FE-SEM S-4800, manufactured by Hitachi, Ltd.).

  The pores of the porous glass obtained by spinodal type phase separation are through-holes connected from the surface to the inside. More specifically, the porous structure derived from spinodal type phase separation is an “ant's nest” -like structure in which pores are entangled three-dimensionally, the silicon oxide skeleton is “nest”, and the through-holes are Corresponds to a “nest hole”. That is, when a porous hole observed with a scanning electron microscope at an acceleration voltage of 5.0 kV and a field of magnification of 150,000 times is a through hole as shown in FIG. 13, spinodal phase separation is performed. The porous structure is derived.

  On the other hand, porous glass obtained by binodal phase separation has a structure in which independent pores, which are pores surrounded by a closed surface close to a sphere, are discontinuously present in the skeleton of silicon oxide. That is, when the pores of the porous structure observed with a scanning electron microscope at an acceleration voltage of 5.0 kV and a field of magnification of 150,000 times are independent pores as shown in FIG. The porous structure is derived.

  The cross-sectional shape of the pores of the porous structure derived from the binodal phase separation is substantially circular. On the other hand, the cross-sectional shape of the pore of the porous structure derived from the spinodal type phase separation has a branched shape, unlike the circular shape. For this reason, in the porous structure derived from spinodal type phase separation, the cross-sectional shape of the skeleton also has a branched shape. In addition, these cross-sectional shapes are a thing at the time of observing in a 150,000 times magnification visual field with the acceleration voltage of 5.0 kV using a scanning electron microscope. In addition, the porous structure by each phase separation is controllable by controlling the composition of a glass body and the temperature at the time of phase separation.

  In the present invention, spinodal type phase separation is utilized. The porous structure derived from spinodal type phase separation has three-dimensional network-like continuous continuous holes connected from the surface to the inside, and the porosity can be arbitrarily controlled by changing the heat treatment conditions. Since this porous structure has a skeleton that is curved and connected in a complicated manner three-dimensionally, it can have high strength even if the porosity is increased. Accordingly, it is possible to provide an optical member having an excellent anti-reflection performance and a strength that is not easily damaged even when touched on the surface because it can have an excellent surface strength while maintaining a high porosity. Is possible.

<Optical member>
As shown in FIG. 1, the optical member of the present invention has a configuration in which a porous glass layer 2 having a porous structure derived from spinodal phase separation in which pores are entangled three-dimensionally is formed on a substrate 1. Since the porous glass layer 2 is a film having a refractive index smaller than that of the substrate 1, reflection at the interface between the porous glass layer 2 and air (the surface of the porous glass layer 2) is suppressed and used as an optical member. There is expected.

  However, in an optical member having a porous glass layer on a base material, interference between the reflected light at the surface of the porous glass layer and the reflected light at the interface between the base material and the porous glass layer interferes with the reflected light. The phenomenon of ripples in which stripes appear is generated. In particular, when the thickness of the porous glass layer is not less than the wavelength of light and not more than several tens of μm, this interference effect is strengthened, so that it appears remarkably.

  Ripple is measured in the form of a sine wave that repeats the intensity almost periodically when the reflectance is measured and the wavelength is plotted on the horizontal axis and the reflectance is plotted on the vertical axis. ing. FIG. 2 shows the reflectance of a structure in which a porous glass layer is formed with a thickness of 1 μm on a quartz glass substrate. If there is such a ripple, the wavelength dependency of the reflectance becomes strong, and may not be suitable as an optical member.

  Therefore, the optical member of the present invention is formed from the base material 1 to the porous glass layer in the thickness direction (X direction in FIG. 1) of the porous glass layer 2 near the interface between the base material 1 and the porous glass layer 2. A configuration in which the substantial porosity increases toward 2 is adopted. More specifically, the structure which has an uneven structure in the interface by the side of the porous glass layer 2 of this base material 1 is taken. Since the porous glass layer 2 is also formed in the concave portion of the concavo-convex structure, the number and volume of holes increase from the base material 1 toward the porous glass layer 2 in the X direction. It becomes the structure which a porosity increases. With this configuration, a sharp change in refractive index at the interface between the substrate 1 and the porous glass layer 2 is suppressed, and reflection at this interface is suppressed. As a result, it is possible to suppress ripples due to interference between the reflected light at the surface of the porous glass layer 2 and the reflected light at the interface between the substrate 1 and the porous glass layer 2.

  The concavo-convex structure of the present invention refers to a structure in which the height of the concavo-convex structure is 100 nm or more in order to suppress ripples. Moreover, the concavo-convex structure of the present invention is a structure in which the width of the convex portion decreases as the distance from the base material 1 increases from the base material 1 side. The height of the concavo-convex structure is the distance between the apex of the adjacent convex portion and the apex of the concave portion in the thickness direction of the porous glass layer 2. When the height of the concavo-convex structure is smaller than 100 nm, the effect of reducing the change in refractive index near the interface between the substrate 1 and the porous glass layer 2 is reduced, and the relationship between the porous glass layer 2 and the substrate 1 is reduced. The effect of suppressing reflection at the interface is reduced. The height of the concavo-convex structure is more preferably 250 nm or more. On the other hand, the upper limit of the height of the concavo-convex structure is equal to or less than the thickness of the porous glass layer 2 formed thereon. Moreover, since the base material 1 is exposed to the surface when the height of the uneven structure is larger than the thickness of the porous glass layer 2, the surface of the porous glass layer 2 is provided by providing the porous glass layer 2. The antireflection effect is reduced.

  In addition, the thickness of the porous glass layer 2 is measured as follows. First, an SEM image (electron micrograph) is taken at an acceleration voltage of 5.0 kV using a scanning electron microscope (FE-SEMS-4800, manufactured by Hitachi, Ltd.). Two or more distances from the photographed image to the top of the concave portion of the concavo-convex structure from the surface of the porous glass layer 2 on the substrate 1 are measured, and the average value is used.

  The thickness of the porous glass layer 2 is not particularly limited, but is preferably 1 μm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less. If it is smaller than 1 μm, it is difficult to obtain an effect of high porosity (low refractive index), and if it is larger than 20 μm, the influence of scattering becomes large, making it difficult to use as an optical member.

  Further, the width of the concavo-convex structure is a minimum value obtained by measuring at least two points between the vertices of two adjacent convex portions. The width of the concavo-convex structure is not particularly limited as long as it has an effect of suppressing ripples, but is preferably 100 nm or more and 2000 nm or less. When the width of the concavo-convex structure is smaller than 100 nm, in the manufacturing method described later, it becomes difficult for the glass powder to enter the recesses, voids are easily formed, and scattering increases. On the other hand, when the width of the concavo-convex structure exceeds 2000 nm (2 μm), the influence of light scattering becomes remarkable and the transmittance is deteriorated.

  The porosity of the porous glass layer 2 is preferably 20% or more and 70% or less, more preferably 20% or more and 60% or less. If the porosity is less than 20%, the advantage of the porousness cannot be fully utilized, and if the porosity is more than 70%, the surface strength tends to decrease, which is not preferable. In addition, that the porosity of the porous glass layer 2 is 20% or more and 70% or less corresponds to the refractive index of 1.10 or more and 1.40 or less.

  The following measurement methods can be used for measuring the porosity. Processing for binarizing the image of the electron micrograph into a skeleton portion and a hole portion is performed. Specifically, using a scanning electron microscope (FE-SEM S-4800, manufactured by Hitachi, Ltd.) at a magnification of 100,000 times (in some cases 50,000 times), which makes it easy to observe the density of the skeleton at an acceleration voltage of 5.0 kV. The surface of the porous glass layer 2 is observed. The observed image is saved as an image, and the image analysis software is used to graph the SEM image at a frequency for each image density. FIG. 3 is a diagram showing the frequency for each image density of the porous spinodal porous structure. The peak portion indicated by the downward arrow of the image density in FIG. 3 indicates a skeleton portion located in front. The bright part (skeleton part) and the dark part (hole part) are binarized into black and white using an inflection point close to the peak position as a threshold value. The average value of all the images is taken for the ratio of the area of the black part to the area of the entire part (the sum of the areas of the white and black parts), and is defined as the porosity.

  The pore diameter of the porous glass layer 2 is preferably 1 nm or more and 100 nm or less, more preferably 5 nm or more and 50 nm or less, and further preferably 5 nm or more and 20 nm or less. If the pore diameter is smaller than 1 nm, the characteristics of the porous structure cannot be fully utilized, and if the pore diameter is larger than 100 nm, the surface strength tends to decrease, which is not preferable. Furthermore, it is preferable that the pore diameter is 20 nm or less because light scattering is remarkably suppressed. The pore diameter is preferably smaller than the thickness of the porous glass layer 2.

  The pore diameter in the present invention is defined as an average value of the minor diameters of approximated ellipses obtained by approximating pores in an area of 5 μm × 5 μm in an arbitrary cross section of the porous body with a plurality of ellipses. Specifically, for example, as shown in FIG. 4A, the hole 10 is approximated by a plurality of ellipses 11 using an electron micrograph of the surface of the porous body, and the average value of the minor axis 12 in each ellipse is obtained. Can be obtained. Measure at least 30 points and find the average value.

  The skeleton diameter of the porous glass layer 2 is preferably 1 nm or more and 100 nm or less, more preferably 5 nm or more and 50 nm or less, and further preferably 5 nm or more and 20 nm or less. When the skeleton diameter is larger than 100 nm, light scattering is conspicuous and the transmittance is greatly reduced. Moreover, when the skeleton diameter is smaller than 1 nm, the strength of the porous glass layer 2 tends to be small. Furthermore, it is preferable that the skeleton diameter is 20 nm or less because light scattering is suppressed.

  The skeleton diameter in the present invention is an average value of the short diameters of the approximated ellipses obtained by approximating a skeleton in an area of 5 μm × 5 μm in an arbitrary cross section of the porous body with a plurality of ellipses. Define. Specifically, for example, as shown in FIG. 4B, the skeleton 13 is approximated by a plurality of ellipses 14 using an electron micrograph of the surface of the porous body, and an average value of the minor axis 15 in each ellipse is obtained. Can be obtained. Measure at least 30 points and find the average value.

  It should be noted that light scattering is influenced uniquely by the thickness of the optical member and the like, and thus is not uniquely determined only by the hole diameter and the skeleton diameter.

  In addition, the pore diameter and skeleton diameter of the porous glass layer 2 can be controlled by the material used as a raw material, heat treatment conditions for spinodal type phase separation, and the like.

  The porous glass layer 2 may further have a configuration in which one layer or a plurality of porous glass layers are laminated on the porous glass layer 2. However, as the whole porous glass layer 2, it is preferable that the porosity increases from the substrate 1 side toward the surface of the porous glass layer because an effect of lower reflectance can be obtained.

  In the optical member of the present invention, a non-porous film having a refractive index smaller than that of the porous glass layer 2 may be provided on the surface of the porous glass layer 2.

  As the substrate 1, a substrate made of any material can be used depending on the purpose. As a material of the substrate 1, for example, quartz glass and quartz are preferable from the viewpoints of transparency, heat resistance, and strength. Moreover, the base material 1 may have a configuration in which layers made of different materials are laminated.

  The substrate 1 is preferably transparent. The transmittance of the substrate 1 is preferably 50% or more in the visible light region (wavelength region of 450 nm or more and 750 nm or less), and more preferably 60% or more. When the transmittance is less than 50%, a problem may occur when used as an optical member.

  The optical members of the present invention are specifically optical members such as various displays such as televisions and computers, polarizing plates used in liquid crystal display devices, finder lenses for cameras, prisms, fly-eye lenses, toric lenses, and the like. Various optical lenses such as a conventional optical system, an observation optical system such as binoculars, a projection optical system used for a liquid crystal projector, a scanning optical system used for a laser beam printer, and the like.

  The optical member of the present invention may be mounted on an imaging apparatus such as a digital camera or a digital video camera. FIG. 5 is a schematic cross-sectional view showing a camera (imaging device) using the optical member of the present invention, specifically, an imaging device for forming a subject image from a lens on an imaging element through an optical filter. . The imaging apparatus 300 includes a main body 310 and a removable lens 320. In an imaging apparatus such as a digital single-lens reflex camera, photographing screens having various angles of view can be obtained by replacing a photographing lens used for photographing with a lens having a different focal length. The main body 310 includes an image sensor 311, an infrared cut filter 312, a low-pass filter 313, and the optical member 314 of the present invention. The optical member 314 includes the base material 1 and the porous glass layer 2 as shown in FIG.

  Further, the optical member 314 and the low-pass filter 313 may be formed integrally or may be separate. Further, the optical member 314 may also serve as a low-pass filter. That is, the base material 1 of the optical member 314 may be a low-pass filter.

  The image sensor 311 is housed in a package (not shown), and this package holds the image sensor 311 in a sealed state with a cover glass (not shown). Further, the optical filter such as the low-pass filter 313 and the infrared cut filter 312 and the cover glass are sealed with a sealing member such as a double-sided tape (not shown). In addition, although the example provided with both the low-pass filter 313 and the infrared cut filter 312 is described as an optical filter, either one may be sufficient.

  Since the surface of the optical member 314 of the present invention has a porous structure, it is excellent in dustproof performance such as dust adhesion suppression. Therefore, the optical member 314 is disposed so as to be located on the side opposite to the imaging element 311 of the optical filter. The optical member 314 is arranged so that the porous glass layer 2 is farther from the imaging element 311 than the base material 1. In other words, the optical member 314 is preferably arranged so as to be positioned in the order of the base material 1 and the porous glass layer 2 from the imaging element 311 side. In addition, the optical member 314 and the imaging element 311 are arranged so that the imaging element 311 can capture an image transmitted through the optical member 314.

  In addition, the imaging apparatus 300 of the present invention may be provided with a foreign substance removing device (not shown) for removing a foreign substance by applying vibration or the like. The foreign matter removing apparatus has a configuration including a vibrating member, a piezoelectric element, and the like.

  The foreign matter removing device may be disposed at any position between the image sensor 311 and the optical member 314. For example, the vibration member may be provided in contact with the optical member 314, the vibration member may be provided in contact with the low pass filter 313, or the vibration member may be in contact with the infrared cut filter 312. It may be provided as follows. In particular, when the optical member 314 of the present invention is provided in contact with the optical member 314, it is difficult for foreign matters such as dust, dirt, and dirt to adhere to the optical member 314, so that the foreign matters can be more efficiently removed.

  Note that the vibration member of the foreign matter removing device may be integrally formed with an optical filter such as the optical member 314, the low-pass filter 313, and the infrared cut filter 312. Further, the vibration member may be constituted by the optical member 314, and may have functions such as a low-pass filter 313 and an infrared cut filter 312.

<Method for producing optical member>
In the method for producing an optical member of the present invention, a glass powder layer containing a plurality of glass powders is formed on a substrate having a concavo-convex structure, and the glass powders of the glass powder layers are fused together to form a base glass. Form a layer. Then, the porous glass layer is formed on the base material by subjecting the base glass layer to a phase separation treatment / etching treatment. In the present invention, in the following, in order to obtain a substrate having a concavo-convex structure, the case where the concavo-convex structure is formed on the base material will be described. Also good.

  Next, each process of the manufacturing method of the optical member of this invention is described in detail using FIG.

[Step of forming a concavo-convex structure on a substrate]
First, as shown in FIG. 6A, an uneven structure is formed on the substrate 1.

  Moreover, as the base material 1, a base material of any material can be used according to the purpose. Examples of the material of the substrate 1 include quartz and quartz. Further, the base material 1 may be a material for a low-pass filter or a lens. Moreover, the base material 1 preferably contains silicon oxide and is not phase-separable. As long as the porous glass layer 2 can be formed, the base material 1 can be used in any shape, and the base material 1 may have a curvature.

  Examples of the method for forming the concavo-convex structure on the substrate 1 include mechanical polishing methods such as blast polishing and barrel polishing, and wet etching methods using a corrosive liquid. Other examples of the method for forming the concavo-convex structure include dry etching methods such as reactive gas etching, reactive ion etching, reactive ion beam etching, ion beam etching, and reactive laser beam etching. Any manufacturing method that can achieve the structure of the present invention can be used alone or in combination.

  In the wet etching method, a corrosive liquid such as Flosstech QEC-FG3 (manufactured by Flosstech) is applied to the entire surface of the substrate 1 where the concavo-convex structure is to be formed, and after a predetermined time has elapsed, it is sufficiently washed with water. That is, an uneven structure is formed. Note that the time for which the surface of the substrate 1 is exposed to the corrosive liquid needs to be adjusted in terms of the reactivity and concentration of the corrosive liquid.

  The mechanical polishing method includes, for example, a method of polishing the surface of the substrate 1 by using a resinoid and rotating the resinoid while adding weight. The load, the number of rotations, and the treatment time may be set as appropriate, but a weight of 0.3 kg or more and 2.0 kg or less is added, a rotation of 30 rpm or more and 80 rpm or less is given, and the treatment is performed for 5 minutes or more and 30 minutes or less. Is desirable.

  In addition to this, as a method of forming the concavo-convex structure, a method of attaching a structure to be a convex portion on the base material 1 by a vapor deposition method or a coating method can be mentioned.

  Examples of the structure serving as a convex portion include fine particles 6 arranged on the substrate 1. That is, as shown in FIG. 15, the step of forming the concavo-convex structure on the substrate 1 includes a step of arranging the fine particles 6 on the substrate 1. Examples of the fine particles 6 include, but are not limited to, colloidal silica, magnesium fluoride, zirconia, antimony oxide, tin oxide, and indium oxide. Among these, colloidal silica and magnesium fluoride are particularly preferable from the viewpoints of transparency and translucency. In addition, as long as the shape of the fine particles 6 can form a porous glass layer in a later step, any shape of the fine particles 6 can be used.

  The softening temperature of the fine particles 6 is preferably equal to or higher than the phase separation temperature of the spinodal type phase separation treatment in the subsequent step, and more preferably equal to or higher than the temperature obtained by adding 100 ° C. to the phase separation temperature. If the softening temperature of the fine particles 6 is lower than the heating temperature of the spinodal type phase separation treatment, the fine particles 6 do not leave a shape after the phase separation treatment, and there is a possibility that no convex portion is formed. The phase separation temperature of the spinodal type phase separation treatment refers to the maximum temperature among the temperatures at which the glass layer derived from the spinodal type phase separation is formed.

  The particle diameter of the fine particles 6 may be in a range in which convex portions having a height of 100 nm or more are formed, and specifically, may be 100 nm or more and 300 nm or less. When the particle size is smaller than 100 nm, the ripple suppressing effect is lowered. When the particle diameter of the fine particles 6 is larger than 300 nm, light scattering increases and the optical member becomes clouded. In the case of the fine particles 6 in this particle size region, a plurality of types of fine particles having different particle sizes may be mixed to form the convex portion.

  The distance between the fine particles 6 is not particularly limited, but is 100 nm or more and 500 nm or less. When the interval between the fine particles 6 is smaller than 100 nm, the glass powder layer in the subsequent process does not enter between the fine particles 6, and voids are generated between the fine particles 6, so that a desired refractive index gradient cannot be obtained. In addition, air gaps cause scattering. On the other hand, if it exceeds 500 nm, there will be many flat portions and a desired refractive index gradient cannot be obtained.

  Examples of the method for arranging the fine particles 6 on the substrate 1 include a method capable of forming the distribution of the fine particles 6 such as a spin coating method, a dip coating method, a printing method, a vacuum deposition method, and a sputtering method. Further, in the step of disposing the fine particles 6 on the base material 1, the fine particles 6 may be formed on the base material 1 together with not only the solvent component but also other components in order to distribute the fine particles 6 without agglomeration. Other components distributed together on the base material 1 are not limited as long as the effect of suppressing ripples can be obtained. For example, fine particles having a smaller particle diameter (complementary fine particles), polymer compounds such as polyvinyl alcohol, polyvinyl pyrrolidone, and polystyrene are preferable.

  As described above, the height of the concavo-convex structure is 100 nm or more, and more preferably 250 nm or more, for the effect of suppressing ripples. Moreover, the upper limit is below the thickness of the porous glass layer 2. In order to facilitate the production of the concavo-convex structure, the height of the concavo-convex structure is preferably 1000 nm or less. That is, the height of the concavo-convex structure is more preferably 250 nm or more and 1000 nm or less. The width of the concavo-convex structure is not particularly limited as long as it has an effect of suppressing ripples, but is preferably 100 nm or more and 2000 nm or less as described above.

  FIG. 7 is a schematic plan view showing an example of the concavo-convex structure formed on the substrate 1. As shown in FIG. 7A, the convex portion of the concavo-convex structure may be conical. Further, the concavo-convex structure may be a structure in which the convex portions are closely packed and arranged on the surface of the substrate 1. Further, as shown in FIG. 7B, the concavo-convex structure may be a structure in which conical convex portions are arranged in a lattice pattern. In addition, as shown in FIG. 7C, the concavo-convex structure may not be a periodic structure, but may be a randomly arranged structure. As shown in FIG. 7D, the convex portion of the concavo-convex structure may be a quadrangular pyramid, or a structure in which the convex portions are arranged in a lattice shape. In addition, the convex portion of the concavo-convex structure may be a triangular pyramid, a truncated cone, a quadrangular frustum, a triangular frustum, a cylinder, a quadrangular prism, or a triangular prism.

  Here, in the case where the projections of the concavo-convex structure are a cylinder, a quadrangular prism, and a triangular prism, if the height of the concavo-convex structure is the same as the thickness of the porous glass layer 2, a sloped structure of porosity is not formed. Ripple is not reduced. For this reason, in such a configuration, it is preferable that the thickness of the porous glass layer 2 be equal to or less than half the thickness of the porous glass layer 2 in order to provide a substantial porosity gradient in the porous glass layer 2.

  That is, in the present invention, the shape of the concavo-convex structure and the height of the concavo-convex structure are adjusted so that a substantial change in porosity is formed near the interface between the porous glass layer 2 and the substrate 1. Has been.

[Step of forming glass powder layer]
Next, as shown in FIG. 6B, a glass powder layer 3 containing glass powder is formed on the surface of the substrate 1 on which the concavo-convex structure is formed.

  In the present invention, it is essential to form the porous glass layer 2 having a porous structure derived from spinodal type phase separation on the substrate 1. For this purpose, precise composition control of the glass is necessary. After the glass composition is once determined, a glass powder having phase separation is produced, and the glass powder is applied onto the substrate 1. A method of forming a film by melting is preferred.

  The phase separation property refers to a property that causes phase separation by heat treatment. Examples of the phase-separable glass include silicon oxide glass I (silicon oxide-boron oxide-alkali metal oxide), silicon oxide glass II (silicon oxide-boron oxide-alkali metal oxide- (alkaline earth metal). Oxide, zinc oxide, aluminum oxide, zirconium oxide)) and titanium oxide glass (silicon oxide-boron oxide-calcium oxide-magnesium oxide-aluminum oxide-titanium oxide). Among them, borosilicate glass of silicon oxide-boron oxide-alkali metal oxide is preferable. Furthermore, in the borosilicate glass, a glass having a composition in which the ratio of silicon oxide is 55.0 wt% or more and 95.0 wt% or less, particularly 60.0 wt% or more and 85.0 wt% or less is preferable. When the ratio of silicon oxide is in the above range, phase-separated glass having a high skeleton strength tends to be easily obtained, which is useful when strength is required. The molar ratio of boron to the alkali component is preferably 0.25 or more and 0.40 or less. When the ratio is out of the range, the film may be broken due to expansion and contraction during etching.

  The basic glass used as the phase-separable glass powder can be produced using a known method except that the raw material is prepared so as to have the above-described phase-separable glass composition. For example, it can be produced by heating and melting a raw material containing a supply source of each component and forming it into a desired form as necessary. The heating temperature in the case of heating and melting may be appropriately set depending on the raw material composition or the like, but it is usually sufficient to heat and melt in the range of 1350 ° C. or higher and 1500 ° C. or lower.

  Thereafter, the basic glass is pulverized to produce glass powder. The pulverization method is not particularly limited, and a known pulverization method can be used. Examples of the pulverization method include a liquid phase pulverization method represented by a bead mill and a gas phase pulverization method represented by a jet mill.

  Examples of the method for forming the glass powder layer 3 include a printing method, a spin coating method, and a dip coating method. Below, it demonstrates, exemplifying the method using the general screen printing method. In the screen printing method, since glass powder is pasted and printed using a screen printer, preparation of the paste is essential. The paste contains a thermoplastic resin, a plasticizer, a solvent and the like together with the glass powder.

  The ratio of the glass powder contained in the paste is 30.0 wt% or more and 90.0 wt% or less, preferably 35.0 wt% or more and 70.0 wt% or less.

  The thermoplastic resin contained in the paste is a component that increases film strength after drying and imparts flexibility. As the thermoplastic resin, polybutyl methacrylate, polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, ethyl cellulose and the like can be used. These thermoplastic resins can be used alone or in combination. The content of the thermoplastic resin contained in the paste is preferably 0.1% by weight or more and 30.0% by weight or less. If it is less than 0.1% by weight, the film strength after drying tends to be weak. If it is larger than 30.0% by weight, it is not preferable because the residual component of the resin tends to remain in the film after fusing.

  Examples of the plasticizer contained in the paste include butylbenzyl phthalate, dioctyl phthalate, diisooctyl phthalate, dicapryl phthalate, and dibutyl phthalate. These plasticizers can be used alone or in combination. The content of the plasticizer contained in the paste is preferably 10.0% by weight or less. By adding a plasticizer, it is possible to control the drying speed and to give flexibility to the dried film.

  Examples of the solvent contained in the paste include terpineol, diethylene glycol monobutyl ether acetate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and the like. These solvents can be used alone or in combination. The content of the solvent contained in the paste is preferably 10.0% by weight or more and 90.0% by weight or less. If it is less than 10.0% by weight, it tends to be difficult to obtain a uniform film. On the other hand, when it exceeds 90.0% by weight, it tends to be difficult to obtain a uniform film.

  The paste can be produced by kneading the above materials at a predetermined ratio.

  After applying such paste on the substrate 1 by screen printing, the solvent component of the paste is dried and removed, whereby the glass powder layer 3 containing glass powder can be formed. Further, the paste may be applied and dried any number of times in order to obtain the desired thickness.

[Process of fusing glass powder]
Subsequently, as shown in FIG. 6C, the glass powders of the glass powder layer 3 are fused together by heating to form a phase-separable base glass layer 4 on the substrate 1.

  The higher the temperature at the time of fusion, the lower the viscosity of the glass and the easier it becomes a flat film, resulting in a film with less scattering on the surface. However, if the temperature at the time of fusion is equal to or higher than the crystallization temperature of the glass powder, the phase-separable base glass layer 4 is crystallized and scattering is caused by this crystal, which causes a decrease in transmittance. For this reason, in this invention, by performing this fusion | melting process by heating at glass transition temperature or more and crystallization temperature or less, glass powder is fuse | melted without crystallizing, and the base glass layer 4 is formed. Can do. Although it varies depending on the difference in the glass composition and the heating rate, specifically, it is preferable to heat at a temperature of 500 ° C. or higher and 800 ° C. or lower. The heating time is preferably 5 minutes to 100 hours.

  Moreover, in order to lose | disappear the formed crystal | crystallization, you may take the method of fusing glass powder at the high temperature of 800 to 1300 degreeC, for example. In this case, even if crystals are generated at the time of temperature rise, the fusion temperature is high, so the crystals themselves are also melted, so that the crystals are unlikely to remain in the base glass layer 4. The heating time is preferably 1 minute to 60 minutes.

  From the viewpoint of obtaining an optical member having a high transmittance, the oxygen concentration at the time of fusion is preferably higher than 20%, and more preferably 50% or higher.

  Examples of the heating method at the time of fusion include electric furnace, oven, resistance heating, infrared lamp heating and the like. Infrared lamp heating is particularly preferable, and it is preferable to heat from the base material 1 by providing a setter such as SiC or Si under the base material 1.

[Step of forming phase separation glass layer]
Next, as shown in FIG. 6D, the phase-separated base glass layer 4 formed on the substrate 1 is heated to form the phase-separated glass layer 5. The phase-separated glass layer 5 here is a glass layer phase-separated into a silicon oxide rich phase and a non-silicon oxide rich phase.

  The heat treatment for phase separation is performed at a temperature of 500 ° C. or higher and 700 ° C. or lower and held for 1 hour or longer and 100 hours or shorter. This temperature and time can be appropriately set according to the pore diameter of the porous glass layer 2 to be obtained. Further, the heat treatment temperature does not have to be a constant temperature, and the temperature may be changed in a continuous step.

  As the heating method, the methods mentioned in the step of fusing the glass powder can be adopted.

[Step of forming porous glass layer]
Next, as shown in FIG. 6 (e), the phase separation glass layer 5 formed on the substrate 1 is etched to form a porous glass layer 2 having continuous pores on the substrate 1. . The non-silicon oxide rich phase can be removed while leaving the silicon oxide rich phase of the phase-separated glass layer 5 by the etching process, the remaining portion is the skeleton of the porous glass layer 2, and the removed portion is porous. It becomes a hole of the glass layer 2.

  The etching process for removing the non-silicon oxide rich phase is generally a process for eluting the non-silicon oxide rich phase, which is a soluble phase, by contacting with an aqueous solution. The means for bringing the aqueous solution into contact with the glass is generally a means for immersing the glass in the aqueous solution, but is not limited as long as it is a means for bringing the glass and the aqueous solution into contact, such as applying an aqueous solution to the glass. As the aqueous solution necessary for the etching treatment, it is possible to use an existing solution that can elute the non-silicon oxide rich phase, such as water, an acid solution, or an alkaline solution. Moreover, you may select multiple types of processes made to contact these aqueous solutions according to a use.

  In general phase-separated glass etching treatment, acid treatment is preferably used from the viewpoint of reducing the load on the insoluble phase (silicon oxide rich phase) and the degree of selective etching. By contacting with an acid solution, the non-silicon oxide rich phase which is an acid-soluble component is eluted and removed, while the erosion of the silicon oxide rich phase is relatively small and high selective etching can be performed.

  As the acid solution, for example, inorganic acids such as hydrochloric acid and nitric acid are preferable. As the acid solution, it is usually preferable to use an aqueous solution containing water as a solvent. What is necessary is just to set the density | concentration of an acid solution suitably in the range of 0.1 mol / L or more and 2.0 mol / L or less normally. In the acid treatment step, the temperature of the acid solution may be in the range of room temperature to 100 ° C., and the treatment time may be 1 hour or more and 500 hours or less.

  Depending on the glass composition, a silicon oxide layer that inhibits etching may occur on the glass surface after the phase separation treatment in the order of several hundred nm. This surface layer can also be removed by polishing or alkali treatment.

  Depending on the glass composition, gelled silicon oxide may be deposited on the skeleton. If necessary, a multi-step etching method using acid etching solutions or water having different acidities can be used. Etching can also be performed at an etching temperature of 15 ° C. or higher and 95 ° C. or lower. If necessary, ultrasonic waves can be applied during the etching process.

  In general, it is preferable to perform water treatment after treatment with an acid solution or an alkali solution. By performing the water treatment, deposits of residual components on the porous glass skeleton can be suppressed, and the porous glass layer 2 having a higher porosity tends to be obtained.

  In general, the temperature in the water treatment step is preferably in the range of 15 ° C to 100 ° C. The time for the water treatment step can be appropriately determined according to the composition, size, and the like of the target glass, but is usually 1 hour to 50 hours.

  EXAMPLES Examples will be described below, but the present invention is not limited to the examples.

<Production example of glass powder>
Mixing of quartz powder, boron oxide, sodium oxide, and alumina so that the feed composition is SiO ₂ 64 wt%, B ₂ O ₃ 27 wt%, Na ₂ O 6 wt%, and Al ₂ O ₃ 3 wt%. The powder was melted at 1500 ° C. for 24 hours using a platinum crucible. Thereafter, the glass was lowered to 1300 ° C. and then poured into a graphite mold. After being allowed to cool in air for about 20 minutes, it was kept in a slow cooling furnace at 500 ° C. for 5 hours and then cooled for 24 hours. A glass body was obtained. The resulting block of borosilicate glass was pulverized using a jet mill until the average particle size became 4.5 μm to obtain glass powder.

<Production example of glass paste>
60.0 parts by mass of the above glass powder α-terpineol 44.0 parts by mass ethyl cellulose (registered trademark ETHOCEL Std 200 (manufactured by Dow Chemical Company))
2.0 parts by weight

  The raw materials were mixed with stirring to obtain a glass paste. The viscosity of the glass paste was 31300 mPa · s.

Example 1
The base material is a product obtained by mirror polishing a quartz base material (made by Iiyama Special Glass Co., Ltd., softening point 1700 ° C., Young's modulus 72 GPa) cut to a size of 50 mm × 50 mm and having a thickness of 1.1 mm. used.

  First, Flosstec QEC-FG3 (manufactured by Flosstec), which is an etching sol solution for glass (corrosive agent), was applied to the surface of the substrate. The sol solution was allowed to stand at 25 ° C. for 30 minutes in contact with the substrate surface, and then the sol solution was removed and washed with water. An uneven structure was formed on the surface of the substrate.

  Then, the said glass paste was apply | coated by screen printing on the surface in which the uneven structure of the base material was formed. The printing machine used was MT-320TV manufactured by Microtech. The plate used was a solid image of 30 mm × 30 mm of # 500.

  Subsequently, it left still for 10 minutes in a 100 degreeC drying furnace, the solvent part was dried, and the glass powder layer was obtained. The thickness of the formed glass powder layer was 10.00 μm as measured by SEM.

  This glass powder layer was heated to 350 ° C. at 5 ° C./min as a resin removal step, and was heat-treated for 3 hours. Next, as a fusing step, the temperature was raised to 700 ° C. at a rate of temperature rise of 5 ° C./min and heat treated for 1 hour to obtain a base glass layer.

  Thereafter, the base glass layer is cooled to 600 ° C. at a temperature decrease rate of 10 ° C./min as a phase separation treatment step, heat-treated at 600 ° C. for 50 hours, and the surface of the obtained film is polished to form a phase separation glass layer. Obtained.

  The phase-separated glass layer was immersed in a 1.0 mol / L aqueous nitric acid solution heated to 80 ° C. and allowed to stand at 80 ° C. for 24 hours. Then, it was immersed in distilled water heated to 80 ° C. and allowed to stand for 24 hours. A glass body was taken out from the solution and dried at room temperature for 12 hours to obtain Sample 1.

  FIG. 8 is a part of a cross-sectional SEM image of Sample 1. When the cross-sectional SEM image was analyzed, the porosity of the porous glass layer was 49%, the pore diameter was 45 nm, and the skeleton diameter was 30 nm.

  Moreover, the uneven structure was formed, the height of the uneven structure was 300 nm, and the space | interval of the uneven structure was 900 nm. The thickness of the porous glass layer was 4.0 μm.

(Example 2)
In this example, Sample 2 was obtained in the same manner as in Example 1 except that the method for forming the uneven structure on the surface of the substrate was different from that in Example 1. In this example, the concavo-convex structure on the substrate was formed by polishing, and a resinoid was used for polishing, and a weight of 1.3 kg was added, and processing was performed for 10 minutes while rotating at 60 rpm.
When the cross section of the sample 2 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 850 nm, the interval between the concavo-convex structures was 950 nm, and the thickness of the porous glass layer was 5.0 μm.
Further, the porosity of the porous glass layer was 49%, the pore diameter was 45 nm, and the skeleton diameter was 30 nm.

(Example 3)
This example differs from Example 1 in that the time for contacting the sol solution with the substrate surface was 60 minutes. Otherwise, Sample 3 was obtained in the same manner as in Example 1.
When the cross section of the sample 3 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 500 nm, the interval between the concavo-convex structures was 700 nm, and the thickness of the porous glass layer was 3.0 μm.
Further, the porosity of the porous glass layer was 49%, the pore diameter was 44 nm, and the skeleton diameter was 31 nm.

Example 4
This example differs from Example 1 in that the time for contacting the sol solution with the substrate surface was 10 minutes. Otherwise, Sample 4 was obtained in the same manner as in Example 1.
When the cross section of the sample 4 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 250 nm, the interval between the concavo-convex structures was 250 nm, and the thickness of the porous glass layer was 3.5 μm.
Further, the porosity of the porous glass layer was 48%, the pore diameter was 44 nm, and the skeleton diameter was 30 nm.

(Example 5)
This example differs from Example 1 in that the time for contacting the sol solution with the substrate surface was 5 minutes. Otherwise, Sample 5 was obtained in the same manner as in Example 1.
When the cross section of the sample 5 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 100 nm, the interval between the concavo-convex structures was 150 nm, and the thickness of the porous glass layer was 3.0 μm.
Further, the porosity of the porous glass layer was 50%, the pore diameter was 45 nm, and the skeleton diameter was 30 nm.

(Example 6)
This example differs from Example 2 in that a weight of 1.3 kg was added and the treatment was performed for 15 minutes while rotating at 60 rpm. Otherwise, Sample 6 was obtained in the same manner as in Example 2.
When the cross section of the sample 6 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 150 nm, the interval between the concavo-convex structures was 2000 nm, and the thickness of the porous glass layer was 5.0 μm.
Further, the porosity of the porous glass layer was 51%, the pore diameter was 46 nm, and the skeleton diameter was 30 nm.

(Example 7)
This example differs from Example 2 in that a 0.7 kg weight was added and the treatment was performed for 15 minutes while rotating at 60 rpm. Otherwise, Sample 7 was obtained in the same manner as in Example 2.
When the cross section of the sample 7 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 950 nm, the interval between the concavo-convex structures was 1500 nm, and the thickness of the porous glass layer was 5.0 μm.
Further, the porosity of the porous glass layer was 49%, the pore diameter was 44 nm, and the skeleton diameter was 28 nm.

(Example 8)
This example differs from Example 2 in that a weight of 0.8 kg was added and the treatment was performed for 15 minutes while rotating at 40 rpm. Otherwise, Sample 8 was obtained in the same manner as Example 2.
When the cross section of the sample 8 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 800 nm, the interval between the concavo-convex structures was 2500 nm, and the thickness of the porous glass layer was 5.0 μm.
Further, the porosity of the porous glass layer was 47%, the pore diameter was 43 nm, and the skeleton diameter was 28 nm.

Example 9
This example is different from Example 1 in that the time for which the sol solution is brought into contact with the substrate surface is 60 minutes, and the temperature at which the sol solution is allowed to stand is 80 ° C. Otherwise, Sample 9 was obtained in the same manner as in Example 1. When the cross section of the sample 9 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the uneven structure was 2000 nm, the interval between the uneven structures was 2200 nm, and the thickness of the porous glass layer was 3.0 μm.
Further, the porosity of the porous glass layer was 48%, the pore diameter was 45 nm, and the skeleton diameter was 29 nm.

(Comparative Example 1)
In this comparative example, a sample 10 was obtained in the same manner as in Example 1 except that the surface treatment with the sol solution was not performed on the surface of the base material.
FIG. 9 is a cross-sectional SEM image of the sample 10. As shown in FIG. 9, it was observed that the porous glass layer was formed, but the uneven structure was not formed on the base material. When a cross-sectional image of Sample 5 was observed with an SEM, a uniform porous glass layer having a thickness of 2.0 μm was formed.
Further, the porosity of the porous glass layer was 48%, the pore diameter was 46 nm, and the skeleton diameter was 30 nm.

(Comparative Example 2)
This comparative example differs from Example 1 in that the time during which the sol solution is brought into contact with the substrate surface was 5 minutes, and the temperature at which the sol solution was allowed to stand was 0 ° C. Otherwise, Sample 11 was obtained in the same manner as in Example 1.
When the cross section of the sample 11 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 80 nm, the interval between the concavo-convex structures was 30 nm, and the thickness of the porous glass layer was 2.5 μm.
Further, the porosity of the porous glass layer was 48%, the pore diameter was 46 nm, and the skeleton diameter was 31 nm.

(Comparative Example 3)
This comparative example differs from Example 2 in that a 0.3 kg weight was added and the treatment was performed for 10 minutes while rotating at 40 rpm. Otherwise, Sample 12 was obtained in the same manner as in Example 2.
When the cross section of the sample 12 was observed by SEM, it was confirmed that an uneven structure was formed. The height of the concavo-convex structure was 800 nm, the interval between the concavo-convex structures was 2500 nm, and the thickness of the porous glass layer was 5.0 μm.
Further, the porosity of the porous glass layer was 48%, the pore diameter was 45 nm, and the skeleton diameter was 31 nm.

<Measurement method of surface reflectance>
Using a lens reflectometer (USPM-RU, manufactured by Olympus Corporation), the surface reflectance of each sample of Examples 1 to 9 and Comparative Examples 1 to 3 is measured every 1 nm in the wavelength range of 400 to 750 nm. did.

  The results of the surface reflectance of Examples 1 to 9 are shown in FIG. 10, and the surface reflectances of Comparative Examples 1 to 3 are shown in FIG. In addition, the reflectance of the quartz glass used for the base material was about 3.3% over the wavelength range of 400 to 750 nm.

  In each sample of Comparative Examples 1 to 3, the difference between the maximum value and the minimum value of the surface reflectance is greater than 1.0 in the above wavelength region, and thus it can be seen that the wavelength dependency of the reflectance is large. On the other hand, in each sample of Examples 1 to 9, the difference between the maximum value and the minimum value of the surface reflectance is 1.0 or less in the above wavelength region, and the wavelength dependency of the reflectance is small.

  In Comparative Example 1, since the uneven structure is not formed at the interface between the base material and the porous glass layer, reflection at the interface between the base material and the porous glass layer is large, and it is considered that ripples are generated.

  In Comparative Examples 2 and 3, although the structure has a concavo-convex structure, the thickness of the porous glass layer is near the interface between the substrate and the porous glass layer because the height of the concavo-convex structure is smaller than 100 nm. It is considered that the ripple was not suppressed because the substantial change in porosity in the direction was steep.

  Furthermore, in Comparative Example 2, since the width of the concavo-convex structure is smaller than 100 nm, it is considered that the glass powder was not penetrated into the concave portion of the concavo-convex structure. Therefore, a gap is formed between the porous glass layer and the substrate, and reflection at the interface between the gap and the substrate, and at the interface between the porous glass layer and the gap is increased, and the reflectance is a comparative example in the above wavelength region. I think that it became larger than 1.

  In Examples 1 to 9, since the height of the concavo-convex structure is 100 nm or more, there is a substantial change in porosity in the thickness direction of the porous glass layer in the vicinity of the interface between the base material and the porous glass layer. It is considered that the ripple is suppressed because it is moderate.

<Evaluation of haze value>
Using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.), the haze values of Examples 1 to 9 and Comparative Examples 1 to 3 were measured and summarized in Tables 1 and 2 below.

  In the samples of Examples 8 and 9, since the width of the concavo-convex structure exceeds 2000 nm (2 μm), scattering by the concavo-convex structure is large.

  In addition, what plotted each sample of an Example and each sample of a comparative example by making a horizontal axis the width | variety of a concavo-convex structure and a vertical axis | shaft is the height of a concavo-convex structure is shown in FIG. The broken line in FIG. 12 is a line having a concavo-convex structure height of 100 nm.

(Examples 10 to 16)
The same substrate as in Example 1 was used.

  First, a solution containing colloidal silica is prepared using isopropyl chloride alcohol as a solvent, and the solution is applied onto the base material by a spin coating method at a film forming process of 5000 rpm for 30 seconds to distribute the colloidal silica on the base material. Arranged. At this time, the particle size of the colloidal silica used in each example is shown in Table 3. In Examples 10 to 12, 15, and 16, supplemental fine particles or polyvinyl pyrrolidone was added in order to distribute the fine particles without aggregating them. Table 3 also shows the added product and the weight ratio of the product to the main fine particles.

  Subsequently, a glass powder layer was formed in the same manner as in Example 1. When the thickness of the formed glass powder layer was measured by SEM, it was 4.00 μm. Thereafter, samples 10 to 16 having a porous glass layer were obtained in the same manner as in Example 1.

  As a result of SEM observation, in samples 10 to 16, a porous glass layer was formed on the substrate, and an uneven structure having a height of 100 nm or more was formed at the interface between the substrate and the porous glass layer. In Samples 10 to 16, for the interval between the fine particles, 40 points were extracted from the SEM photograph near the interface, and the minimum and maximum values were measured. It described in Table 3.

  FIG. 16 is a part of a cross-sectional SEM image of the sample 10. When the cross-sectional SEM image F was analyzed, the porosity of the porous glass layer was 52%, the pore diameter was 41 nm, and the skeleton diameter was 36 nm.

  Using a lens reflectometer (USPM-RU, manufactured by Olympus Corporation), the surface reflectance of each sample of Examples 10 to 16 was measured every 1 nm in the wavelength range of 400 to 750 nm. The result is shown in FIG.

  In addition, the reflectance of the quartz glass used for the base material was about 3.3% over the wavelength range of 400 to 750 nm as described above.

  In each sample of Examples 10 to 16, the difference between the maximum value and the minimum value of the surface reflectance is about 1.0 or less in the above wavelength region, and the wavelength dependency of the reflectance is small.

DESCRIPTION OF SYMBOLS 1 Base material 2 Porous glass layer 3 Glass powder layer 4 Base glass layer 5 Phase separation glass layer

Claims (17)

An optical member comprising a base material and a porous glass layer formed on the base material,
A concavo-convex structure is formed at the interface in contact with the porous glass layer of the substrate,
The height of the uneven structure is not less than 100 nm and not more than the thickness of the porous glass layer.   The optical member according to claim 1, wherein a height of the concavo-convex structure is 250 nm or more and 1000 nm or less.   The optical member according to claim 1, wherein a width of the uneven structure is 100 nm or more and 2000 nm or less.   The optical member according to any one of claims 1 to 3, wherein the porous glass layer has a porous structure in which pores are entangled three-dimensionally.   The optical member according to claim 1, wherein the concavo-convex structure is formed of fine particles.   The optical member according to claim 5, wherein a particle diameter of the fine particles is 100 nm or more and 300 nm or less.   An image pickup apparatus comprising: the optical member according to claim 1; and an image pickup device that picks up an image transmitted through the optical member.   The image pickup apparatus according to claim 7, wherein the optical member is arranged in order of the base material and the porous glass layer in order from the image pickup element side. A method for producing an optical member comprising a substrate and a porous glass layer formed on the substrate,
Obtaining a substrate having a concavo-convex structure;
Forming a porous glass layer on the surface of the concavo-convex structure of the substrate,
The method for producing an optical member, wherein the concavo-convex structure has a height of the concavo-convex structure of not less than 100 nm and not more than the thickness of the porous glass layer.   The method for manufacturing an optical member according to claim 9, wherein a height of the uneven structure is 250 nm or more and 1000 nm or less.   11. The method for manufacturing an optical member according to claim 9, wherein the uneven structure has a width of 100 nm or more and 2000 nm or less.   The method for producing an optical member according to any one of claims 9 to 11, wherein the step of obtaining the base material having the concavo-convex structure includes a step of forming the concavo-convex structure on the base material.   The method of manufacturing an optical member according to claim 12, wherein the step of forming the concavo-convex structure includes a step of etching the surface of the base material by a wet etching method.   The method for producing an optical member according to claim 12, wherein the step of forming the concavo-convex structure includes a step of polishing the surface of the substrate to form the concavo-convex structure.   The method of manufacturing an optical member according to claim 12, wherein the step of forming the concavo-convex structure is a step of arranging fine particles on the base material.   The method for producing an optical member according to claim 15, wherein a particle diameter of the fine particles is 100 nm or more and 300 nm or less. The step of forming the porous glass layer includes
Forming a glass powder layer containing a plurality of glass powders on the concavo-convex structure;
A step of fusing together a plurality of glass powders of the glass powder layer to form a phase-separable base glass layer;
A step of phase-separating the base glass layer to form a phase-separated glass layer;
The method for producing an optical member according to claim 9, further comprising: etching the phase separation glass layer to form the porous glass layer.